_functions.scss

/**
 * Color contrast function
 * https://codepen.io/davidhalford/pen/ALrbEP
 */
@function color-contrast($color, $dark: #000, $light: #fff) {
    $color-brightness: round(math.div((red($color) * 299) + (green($color) * 587) + (blue($color) * 114), 1000));
    $light-color: round(math.div((red(#ffffff) * 299) + (green(#ffffff) * 587) + (blue(#ffffff) * 114), 1000));

    @if abs($color-brightness) < ($light-color * .5) {
        @return $light;
    } @else {
        @return $dark;
    }
}